The invention resides in a method of controlling an internal combustion engine including a common rail fuel injection system with individual storage chambers, wherein an actual injection end is determined from the pressure pattern of the individual storage chambers and a virtual injection begin is determined.
In an internal combustion engine, the start and the end of the fuel injection determine to a large extend the quality of the combustion and the composition of the exhaust gas. In order to maintain legal limits, these two characteristic values are generally controlled by an electronic control unit. In practice, however, there is the problem that, in an internal combustion engine with a common rail system, there is always some time delay between the start of the energization of the injectors, that is the injector needle actuation and the actual fuel injection begin. Correspondingly, the same is true for the fuel injection termination.
DE 198 50 221 C1 discloses a method for the examination of an injector. Herein, different injector operating points are determined by varying the pressure of the injector outlet while the inlet pressure is maintained constant. The injector is in good operating condition, that is, it is fault free, if the operating points are within a reliable area of a test performance graph. The testing procedure is used on an injector testing bench. It cannot be used when for injectors while they are installed in an internal combustion engine.
German Patent Application DE 103 44 181.6 (which is not a prior art document) discloses a method of controlling an internal combustion engine wherein from the pressure pattern in an individual storage chamber of a common rail fuel injection system, the end of the fuel injection is detected. From the measured end of the fuel injection then, via a mathematical function, a virtual injection begin is calculated. However, changes of injector properties over the operating life of an injector are not taken into consideration with the method.
It is the object of the present invention to provide for an internal combustion engine with a common rail fuel injection system including individual storage chambers a testing method for the fuel injectors of the engine with the injectors mounted to the engine.